1. Field of the Invention
The invention relates to a piston pump with at least one piston element, which can be driven by a drive unit and is situated in a longitudinally moving fashion inside a housing.
2. Description of the Prior Art
WO 01/81761 A1 has disclosed a piston pump with two piston elements that can be driven by a drive unit and are situated in a longitudinally moving fashion inside a housing. Together with a housing, the piston elements each define a respective pressure chamber whose volume varies as a function of a piston movement. The pressure chambers are connected to both the suction side or a suction region and the pressure side or a delivery side of the piston pump; during a suction stroke of the piston elements, hydraulic fluid is drawn into the relevant pressure chamber, which is characterized by a steady volume increase, and during a delivery stroke of the piston element, hydraulic fluid is conveyed in the direction of the delivery side from the pressure chamber, which is then characterized by a steady volume decrease. In addition, the delivery side of the piston pump is respectively connected to a working piston chamber of a compensation piston unit whose compensation piston is likewise moved by the drive unit, back and forth in the longitudinal direction in the housing, between a top dead center and a bottom dead center.
In order to smooth a pressure pulsation on the delivery side of the piston pump, the piston element and the compensation piston unit corresponding to it are respectively phase shifted in relation to each other by 180° so that the compensation piston of the compensation piston unit is situated in its bottom dead center when the corresponding piston element is situated in its top dead center.
In addition, the compensation pistons are embodied as stepped in order to smooth a suction-side pressure pulsation of the two-piston pump in comparison to conventional two-piston pumps not equipped with compensation pistons. This is based on the knowledge that the suction-side delivery characteristic of a piston pump can be smoothed through the use of a so-called step-piston pump essentially to the same degree as the pressure-side delivery characteristic can be smoothed by the combination of the pump piston elements with the compensation pistons.
It is disadvantageous, however, that the piston rod, which cooperates with a cam of the drive unit, limits the effective area of the stepped compensation pistons used to smooth the suction-side pressure pulsations, in such a way that a desired smoothing of the suction-side pressure pulsation cannot be achieved to the extent desired.